Description of problem:
when running 'tail -f' on some scenarios, it is failing to show new contents on files.

Version-Release number of selected component (if applicable):

2.6.32-112.el6.x86_64

How reproducible:
Always.



Steps to Reproduce:
Run the following script:
----------------
#!/bin/bash
f=/tmp/tail-test
echo file: $f
echo ok > "$f"
sleep 1
tail -f "$f" &
sleep 1
echo ok2 > "$f"
wait
------------------


Actual results:
tail shows "ok"


Expected results:
tail shows "ok" and "ok2" lines.


Additional info:
strace output:


[pid 30838] inotify_init()              = 4
[pid 30838] inotify_add_watch(4, "/tmp/tail-test", IN_MODIFY|IN_ATTRIB|IN_DELETE_SELF|IN_MOVE_SELF) = 1
[pid 30838] fstat(3, {st_mode=S_IFREG|0644, st_size=3, ...}) = 0
[pid 30838] read(4,  <unfinished ...>
[pid 30839] <... nanosleep resumed> NULL) = 0
[pid 30839] close(1)                    = 0
[pid 30839] close(2)                    = 0
[pid 30839] exit_group(0)               = ?
Process 30835 resumed
Process 30839 detached
[pid 30835] <... wait4 resumed> [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0, NULL) = 30839
[pid 30835] rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
[pid 30835] --- SIGCHLD (Child exited) @ 0 (0) ---
[pid 30835] wait4(-1, 0x7fff9ffbc25c, WNOHANG, NULL) = 0
[pid 30835] rt_sigreturn(0xffffffffffffffff) = 0
[pid 30835] rt_sigaction(SIGINT, {SIG_DFL, [], SA_RESTORER, 0x3bb2e32a20}, {0x43d220, [], SA_RESTORER, 0x3bb2e32a20}, 8) = 0
[pid 30835] rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0
[pid 30835] read(255, "echo ok2 > \"$f\"\nwait\n", 110) = 21
[pid 30835] write(2, "+ echo ok2\n", 11+ echo ok2
) = 11
[pid 30835] open("/tmp/tail-test", O_WRONLY|O_CREAT|O_TRUNC, 0666) = 3
[pid 30835] fcntl(1, F_GETFD)           = 0
[pid 30835] fcntl(1, F_DUPFD, 10)       = 10
[pid 30835] fcntl(1, F_GETFD)           = 0
[pid 30835] fcntl(10, F_SETFD, FD_CLOEXEC) = 0
[pid 30835] dup2(3, 1)                  = 1
[pid 30835] close(3)                    = 0
[pid 30835] write(1, "ok2\n", 4)        = 4
[pid 30835] dup2(10, 1)                 = 1
[pid 30835] fcntl(10, F_GETFD)          = 0x1 (flags FD_CLOEXEC)
[pid 30835] close(10)                   = 0
[pid 30835] rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0
[pid 30835] write(2, "+ wait\n", 7+ wait